Infrared imaging is used to locate cold or hot spots in commercial buildings, residential houses or to monitor heat variation of the information technology (IT) chip temperatures. Infrared imaging may be the easiest way to monitor the health and performance of large installations like solar farms where parts of the installation are not operating at the optimum levels. High temperatures (overheating) across a certain location(s) of a solar panel can indicate mechanical, electrical wiring, or photovoltaic performance shortcomings. Large scale temperature measurements are also becoming very valuable in agriculture where crop temperatures are direct indicators of the evapotranspiration processes and also of the vigor of the crops. Satellite or airborne imaging techniques may be used for these applications but they tend to be expensive and lack the spatial resolution (spatial pixel size tend to be 10 meters or higher). Furthermore, with satellite or airborne imaging the data will be acquired at large time intervals reducing the usefulness of techniques to identify and troubleshoot problems in real-time.
Another area where local temperature is important is with large scale solar installations where solar panels are mounted is a series-parallel configuration—such that a number of panels are mounted as a string in series to increase the voltage (e.g., greater than 600 VDC in the United States) and then the string of solar panels are mounted in parallel to increase the current.
In a solar system, solar panels strings coupled with inverters are used to collect and convert solar energy into electricity. Specifically, a central DC-AC inverter is used to convert the DC output from the solar panels into electricity. Many of the central inverters operate more efficiently at larger voltage and current inputs and this drives the solar panel connections to operate the inverters at their maximum performance.
In many situations, the performance of individual solar panels can be diminished due to mounting errors which will affect the performance of the whole panel string and thus reduce the overall system performance. Factors that affect individual solar panel performance can be solar sub-cell defects or wiring/interconnect issues that result in solar panel overheating. Once the temperature of a defective solar panel increases, the overall performance of the solar installation is reduced (i.e., the power produced decreases with increased panel temperature) as current flow through the strings of panels can be constrained or cut-off by a defective cell in the solar panel. Mounting/installation errors can also affect performance. For example, shadowing due to nearby structures leads to reduced voltage/current performance of solar panels.
Shadowing has more of an effect in the case of series mounted solar panel strings when the resistance of the solar panels is increased (the current drops) reducing the performance of the string of panels. Furthermore shadowing can result in voltage output fluctuations leading to unstable operation of inverters. Either solar panel overheating (increased temperature) or shadowing can result in reduced performance.
Thus, techniques for monitoring large scale solar installations in order to locate underperforming solar panels would be desirable.